The present invention relates generally to welding-type systems and, more particularly, to an apparatus for improved high-frequency arc starting of a welding process.
There are a large number of welding processes available for use in industry. For example, some welding processes include gas tungsten arc, oxygen gas welding, and shielded metal arc welding. The gas tungsten arc welding process is generally referred to as tungsten inert gas (TIG) welding. A typical TIG welding apparatus includes a welding component that is commonly referred to as welding torch and is designed to control a tungsten electrode during a welding process. The electrode is heated to extremely high temperatures by electrical power received from the power supply. At appropriate voltage and current, a welding arc is created between the electrode and a workpiece to be welded.
It is well known that TIG welding is often preferably started using a high-frequency (HF) starting system. High-frequency starting is a method of generating an arc without moving parts or the wear associated with shorting and breaking. To perform HF starting, a welding torch is connected to a power supply having an HF starting circuit. The circuit typically includes a high-voltage transformer, capacitors for power conditioning, and a nozzle assembly configured to generate a high-voltage spark at the torch electrode. When sufficient voltage is provided by the power supply to the torch, a spark fires from the electrode and traverses a gap between the electrode and the workpiece.
However, while HF starting systems serve to protect the electrode from the wear associated with shorting and breaking of a contact starting system, it is often less reliable than contact starting systems. For example, it is not uncommon that HF starting of a TIG welding process may fail on more than 25% of starts.
As such, some operators have attempted to improve the reliability of HF starting by decreasing the distance between the electrode and workpiece during the HF start. However, as the gap between the electrode and workpiece is decreased, the probability of the electrode contacting the workpiece increases. Should the electrode strike the workpiece, the advantage of decreased wear afforded by HF starting is removed. Furthermore, in TIG welding processes, should the tungsten electrode strike the workpiece, some of the tungsten may be transferred to the workpiece and reduce the integrity of the weld.
Accordingly, some operators have designed a way to “move” the workpiece electrically closer to the electrode without reducing the gap between the electrode and the workpiece. That is, some operators have connected a wire from the workpiece to the nozzle where it is clamped thereto. While this piecemeal system increases HF starting performance it has many drawbacks.
Specifically, the system is insecure, unstable, and may be unintentionally separated or dismantled during normal welding operations. That is, these systems are prone to inadvertently disassembly because the wire connecting the workpiece to the nozzle is merely clamped in place and dangling from the welding torch. As such, the wire may be inadvertently removed from the clamp or may interfere with the welding process. Furthermore, the clamp may obscure the operator's view of the workpiece or interfere with the welding process. Additionally, the clamp may be easily moved or dislodged from the nozzle during normal welding operations.
Also, the clamp securing the wire to the nozzle, while integral in creating the advantages of these piecemeal systems, is undesirable. That is, the clamp is electrically charged and, therefore, creates a system that may not comply with applicable workplace standards and regulations.
Furthermore, the welding cable and the wire connecting the workpiece and nozzle carry a potential difference equal to the potential difference between the tungsten electrode and the workpiece desired for effectuating a welding process. This relatively high potential difference can result in leakage of the HF voltage and diminish the peak voltage available to establish an initial welding arc if the welding cable and the wire leading from the workpiece to the nozzle are too close in proximity.
Therefore, it would be desirable to have a system and method for improving the consistency of HF starting that does not interfere with initiating a welding arc, does not interfere with the welding process, is not susceptible to inadvertent movement or disassembly, and is compliant with acceptable workplace standards and regulations.